As one of medical treatments for curing a serious heart disease patient, treatment which uses an implantable blood pump has been performed. To appropriately perform the treatment, it is necessary to accurately find a flow rate of the blood pump. Accordingly, a blood flow meter such as a blood flow meter based on a thermodilution method, a blood flow meter based on a dye dilution method, an electromagnetic blood flow meter, an ultrasonic blood flow meter, a blood flow meter based on a transesophageal echocardiography, a blood flow meter based on a transthoracic echocardiography or a blood flow meter based on an electric impedance method is mounted inside or outside a body of a patient, and the flow rate of the implantable blood pump is measured.
However, with respect to the blood flow meter such as the blood flow meter based on the thermodilution method, the blood flow meter based on the dye dilution method, the electromagnetic blood flow meter or the ultrasonic blood flow meter, it is necessary to mount such a blood flow meter inside the body of the patient, and hence, the use of the blood flow meter is considerably invasive to the patient. Accordingly, the mounting of the blood flow meter inside the body of the patient is limited for a certain period postoperatively in an actual use, and hence, after removing the blood flow meter from the body of the patient, a method which allows a user to know the flow rate of the blood pump without using the blood flow meter becomes necessary.
In addition, with respect to the blood flow meter such as the blood flow meter based on the transesophageal echocardiography, the blood flow meter based on the transthoracic echocardiography or the blood flow meter based on the electric impedance method, steps for measuring the flow rate of blood are cumbersome in an actual operation, and hence, it is also fairly invasive to the patient. Accordingly, a method which allows a user to know the flow rate of the blood pump without using the blood flow meter also becomes necessary.
FIG. 14 and FIG. 15 are views for explaining a conventional blood pump system which satisfies such demands as mentioned above.
The conventional blood pump system 901 includes, as shown in FIG. 14 and FIG. 15, a blood pump 905 which discharges blood by rotating an impeller 921 by making use of a rotational force of a motor 934 as a driving power source, a viscosity/rotational-speed/motor-current/discharge-flow-rate related data storing part 960 which stores “predetermined viscosity-related discharge-flow-rate data” which is constituted of various motor current/discharge flow rate related data at various different impeller rotational speeds under a predetermined liquid viscosity with respect to various different predetermined viscosities, a blood parameter input part 957, a sensor circuit 955 which has a function of measuring and calculating an impeller rotational speed which measures the rotational speed of the impeller 921, a motor current measuring part which has a function of measuring a current supplied to the motor 934, and a discharge flow rate arithmetic calculation part 958 which calculates a liquid discharge flow rate based on liquid viscosity, a motor current and an impeller rotational speed using the liquid viscosity, the impeller rotational speed, the motor current, and viscosity/rotational speed/motor current/discharge flow rate related data (for predetermined viscosity-related discharge-flow-rate data table, see FIG. 15).
According to the blood pump system 901, as shown in FIG. 14 and FIG. 15, since the impeller rotational speed, the motor current and the blood viscosity are measured and, thereafter, a blood discharge flow rate is calculated based on the measured values and the predetermined viscosity-related discharge-flow-rate data table, the flow rate of the blood pump can be estimated without using any blood flow meter.
Further, according to the blood pump system 901, as shown in FIG. 14 and FIG. 15, since the blood discharge flow rate is calculated based on the predetermined viscosity-related discharge-flow-rate data table, that is, the minimal number of individual data which satisfies the required accuracy is stored as a data table and the blood discharge flow rate is calculated selectively using the data close to a current value to be calculated or the like, the accurate flow rate can be easily obtained in comparison with a case that the blood discharge flow rate is calculated based on a relationship formula of the impeller rotational speed, the motor current, the blood viscosity, and the flow rate of the blood pump (see patent document 1, for example).
[Patent Document 1]
JP-A-2003-210572